How much money would it take to get an English major to switch to engineering? Would a $1,000 discount on tuition every year do the trick? What about $5,000? What if switching majors not only reduced students’ debt load but also made it much more likely that they would find a job after graduation? Would that be enough to change their mind?

These are questions Florida is debating as it looks for ways to steer more students into high-paying fields that employers are eager to cultivate. Governor Rick Scott’s task force on higher education recently suggested freezing tuition at state schools in “strategic areas” like engineering, science, health care and technology, while letting the cost of humanities and other majors rise.

The Florida proposal is a new twist on an old idea. Instead of increasing tuition across the board, many universities over the past decade have started charging more for majors with courses that are more costly to provide. Degrees in biology and engineering, for example, typically involve smaller class sizes, higher faculty salaries and cutting-edge labs with expensive equipment, so universities look to students to foot more of the bill. Today some 45% of large public research universities differentiate their pricing this way. At the University of Texas at Austin, which started charging different tuition rates in 2004, engineering students pay $5,107 each semester, while liberal-arts majors pay $4,673. (That’s for in-state residents; for out-of-staters, the tuition costs jump to $17,189 and $15,878, respectively.)

Kevin Stange, a professor of public policy at the University of Michigan, studies the outcomes of differential tuition and has found that higher prices tend to dissuade students. The generally accepted consensus is that a $1,000 change in costs is associated with a 5 percentage point difference in enrollment rates. Similarly, a June study from Hanover Research found that for every $100 increase in tuition, enrollment decreased by 0.5% to 1%.

“When institutions start charging more for engineering and business, we do see a decline in the number of students pursuing those degrees,” Stange said. But he thinks it’s unlikely that lowering tuition will persuade huge numbers of people to major in such rigorous, technical fields. “Getting humanities majors to become engineering majors is probably a stretch.”

Past attempts by the government to push students toward the sciences and math have had underwhelming results. In 2005 Congress approved a government grant program, known as the National SMART grants, that was designed to use additional financial aid as a carrot to encourage more low-income students to major in science, technology, engineering and math (STEM). Qualifying students could receive as much as $4,000 a year on top of their Pell Grants. But getting low-income students into STEM fields was tough — the program never met its participation targets and was cut in 2010–11.

“People tend to pursue what they’re most comfortable with, so lower-income students are drawn toward teaching and social sciences,” says Tom Mortenson, a policy analyst at the Pell Institute for the Study of Opportunity in Higher Education. “You don’t bump into engineering by accident. It requires a serious commitment to education and a more structured path to get there.”

Motivating students to pursue degrees in technical fields remains an uphill battle, despite increasing demand for STEM majors. A White House report released in February estimated that the U.S. will need 1 million additional STEM graduates over the next decade in order to fill the growing number of jobs that require those skills, yet student interest remains low. The report, drafted by the President’s Council of Advisors on Science and Technology, found that fewer than 40% of students who enter college intending to major in STEM fields complete a STEM degree.

Many prospective college students aren’t even considering studying math or science. An online survey commissioned by the University of Sciences in Philadelphia and conducted in April by Harris Interactive found that 51% of high schoolers weren’t interested in pursuing careers in the sciences or health care, 21% said they felt they were not good at the subjects and 16% said they did not feel ready to study science or health care in college. “The problem is not that students are uninterested in STEM fields but that they are unprepared,” Sherman Dorn, a professor in the College of Education at the University of South Florida, wrote in a blog post. “How many undergraduates in Florida start out wanting to be doctors and are absolutely certain they are going to be doctors until they hit calculus and organic chemistry?”

Cheaper tuition might motivate some students to tough it out, but Timothy Wilson, a professor of psychology at the University of Virginia and author of Redirect: The Surprising New Science of Psychological Change, urges schools and policymakers to proceed with caution. “There is some evidence that external incentives lower internal motivation,” he says. “There’s a danger if people are doing something just because it’s cheaper. Engineering is a very challenging field. People need to be really into it — it’s not something you can do just for the money.”